Apparatus for producing base tones in an electronic musical instrument

ABSTRACT

An apparatus for producing base tones in an electronic musical instrument adapted to produce base tones by successively frequency dividing a base tone signal selected by a single tone selection circuit by 1/2 frequency dividers to obtain a plurality of foot-register signals and providing these footregister signals with desired envelope and tone-color. The base tone to be obtained is provided with a &#39;&#39;&#39;&#39;sway&#39;&#39;&#39;&#39; effect either by phase-modulating a base tone signal by a modulating signal of about 1 Hz, by phase-modulating each foot-register signal in the same phase or in different phases by a modulating signal of about 1 Hz, or by phase-modulating the output signal of a tone-color circuit by a modulating signal of about 1 Hz. In one form of the inventive apparatus, the base tone signal is fed to two separate systems. In this case, the phase modulation is carried out in one of the systems and not in the other. The phase modulation may also be carried out in both systems in which case modulating signals differing in phase by 180* from each other are used for the phase modulation.

United States Patent 1191 Adachi APPARATUS FOR PRODUCING BASE [111 3,835,236 [451 Sept. 10, 1974 3,740,449 6/1973 Southard 84/ 1.17 TONES IN AN ELECTRONIC MUSIC INSTRUMENT Primary Examiner-Richard B. Wilkinson Assistant Examiner-U. Weldon [75] Inventor: Takeshl Adachl, Hamamatsu, Japan Attorney, Agent, or Firm Ladas, Parry, Von Gehr, [73] Assignee: Nippon Gakki SeizoKabushiki l mi h & D s hamps Kaisha, Shizuoka-ken, Japan 22 Filed: Aug. 29, 1973 L f g T i I n apparatus or pro ucmg ase tones 1n an e ec- [211 App! 392401 tronic musical instrument adapted to produce base tones by successively frequency dividing a base tone [30] Foreign Application Priority Data signal selected by a single tone selection circuit by b Aug 30 1972 Japan 47 101224[U] 7 frequency dividers to obtain a plurality of foot-register Aug. 30 1972 Ja an 47-101225[U] Signals and Prbyiding these fbbt'register signals with Aug. 30 1972 Japan 47-101226[U] desired envelope and tbbe'bblm- The base to be Aug. 30 1972 Ja an 47-101'227 u bbtained is Pmyided with a effect either by Aug. 30 1972 Japan 47-101228[U] I bbase'mbdblabng a base signal by a modulating Aug. 30 1972 Ja an 47-101229w Signal of about 1 HZa-by pbase'mbdblating each foot- Aug 1972 Japan 47 10l23O[U]- register signal in the same phase or in different phases Aug: 30 1972 Japan: 1.131.: 47-1o1231w by a mbdulating Signal of abbbt 1 by P modulating the output signal of a tone-color circuit by 52 us. 01 84/l.24 84/1.17 84/l.ll a modulating Signal of about 1 In one form of the 51 Int. Cl. G 10h 1/02 inventive apparatus, the base tone Signal is fed to two [58] Field of Search 84/101 103 L08, L11 separate systems. In this case, the phase modulation is A 84/1 L24, DIG-,4 carried out in one of the systems and not in the other. The phase modulation may also be carried out in both [56] References Cited systemsm whlch case modulatlng slgnals differing in phase by 180 from each other are used for the phase UNITED STATES PATENTS modulation. 3,000,252 9/196! Wayne 84/l.17 x 3,598,892 8/1971 Yamashita 84/l.0l 12 Claims, 18 Drawing Figures LATCHING 8 PHASE cc c 2 SELECTOR MODU- 42 43 l LATOR a 2 a z 1 1 53 KEYER 9 OSCIL- LATOR 6 TONE f COLOR {PK 52 PEDAL. KEYER' KEYER KEYBOARD Pmmwsm 1w Y 3.335.236

SHEET 1 OF 9 'F|G. l PRIOR ART (UK U| p LK U2 7 I0 In F L; "J

PRIOR ART cc c 2 3 4| 42 43 1-------4/ r r r L L 5| 52 53 6 PK PATENIED SEP 1 mm SHEET 5 [IF 9 PAIENTEU T 3.835.236

susenurs FIG. l2

BACKGROUND'OF THE INVENTION This invention relates to an apparatus for producing base tones in an electronic musical instrument.

In an electronic musical instrument base tones are necessary for beating basic rhythms and supporting harmonics, being generally produced by depression of pedals. In a pedal circuit of conventional electronic musicalinstrument as illustrated in FIG. 1, signals from tone generator 1 are applied to a latching selector (single" tone selection and storing circuit such as shown in US. Pat. 3,598,892) 2 which memorizes and delivers a single tone selected by one of pedals PK out of a plurality of tone signals input thereto. The output delivered from this latching selector 2 is applied to a frequency divider 4 through an amplifier 3.. The frequency divided output from the frequency divider 4 is applied to a tone keyer (envelope circuit) 5 and thereafter is fed to a tone-color circuit 6 in which the signal is provided with a desired tone-color. The output of the tonecolor circuit 6 is amplified at an amplifier 7 (including an expression control) and thereafter is sounded from a loud speaker 10. The latching selector 2 selects only one tone signal corresponding to the depressed key in the pedal keyboard PK from among a plurality of tone signals from the tone generators, connecting the signal to its output terminal and keeping that connection until a next tone is selected by depression of another pedal. More specifically, the pedal circuit has, as shown in FIG. 2, a frequency dividers 41-43 connected in tandem at a post stage of the amplifier 3 for producing signals of 4', 8' and 16' registers. These signals of 4', 8' and 16' registers are respectively supplied to tone keyers 5l53. The outputs of these tone keyers 51-53 are applied to the tone-color circuit 6 in which a base tone of a desired tone-color is produced from these outputs. In an upper keyboard circuit tone signals pass through an upper keyboard UK (including key switches and keyers) and a tone-color circuit U to the amplifier 7, whereas in a lower keyboard circuit tone signals pass through a lower keyboardLK (including key switches and keyers) and a tone-color circuit U to the amplifier 7. Thus, the upper and lower keyboard tones as well as the pedal tones are sounded from thespeaker 10.

The base tones produced by the conventional electronic musical instruments generally have a constant pitch without being subjected to any change while they are sounded. v 7 It has been found, however, that the listener perceives monotonousness and lack in naturalness from such base tones of a constant pitch. The base tones of natural musical instruments .are conspicuously perceived by the listener because they have a slight fluctuation in their pitches (hereinafter called sway) while they are being sounded. The base tones sounded by the conventional electronic musical instrument which have no such sway have been found too stable to produce a sufficient semblance of the base tones of natural musical instruments.

SUMMARY OF THE INVENTION cal instrument capable of producing base tones closely resembling those of natural musical instruments by giving them a sway effect. It is another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing base tones which are provided with a sway effect by phase-modulating a base tone signal with a modulating signal of about 1 1-12.

It is another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing base tones having a sway effect by utilizing beat which occurs between a base tone signal and a signal obtained by applying a phase modulation of approximately 1 Hz to the base tone signal when these two signals are simultaneously sounded.

It is another object of the invention to provide an apparatus for producing base tones in an electronic musiproducing base tones having a sway efiect by feeding a base tone signal to two systems, phase-modulating these signals by modulating signals of approximately 1 Hz difiering in phase by from each other and sounding the phase-modulated signals simultaneously.

It is another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing a concerted music effect by obtaining base tones in which harmonic overtones have a sway with respect to a fundamental tone and thereby giving a sway effect to each tone-color.

It is another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing base tones which have a continuous sway for a certain extended period of time from the start of sounding and thereby producing a close semblance to the base tones of natural musical instruments.

It is another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing base tones in which the fundamental tone and the harmonic overtones have different sways with a result that naturalness and richness are given to the tone, as well as producing a concerted music effect by sounding all foot-register signals directly and simultaneously thereby emphasizing the sway effect by comparison of the respective tones.

It is another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing base tones of an increased naturalness in which the fundamental tone and the harmonic overtones have different sways with a greater extent of sway being given to the harmonics as the degree of harmonics increases.

It is still another object of the invention to provide an apparatus for producing base tones in an electronic musical instrument capable of producing base tones of an increased naturalness and variety in which the fundamental wave component and each harmonic component are provided with different sways by varying phase relations between these components.

Other objects and features of the invention will become apparent from the description made hereinbelow with reference to the accompanying drawings, wherein like numerals designate corresponding component parts in the several figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are block diagrams respectively showing typical examples of the prior art apparatusfor producing base tones in'an electronic musical instrument;

FIG. 3 is a block diagram showing one preferred embodiment of the apparatus for producing base tones in an electronic musical instrument according to the invention;

FIG. 4(a) is a blockdiagram showing a phase modulation circuit in FIG. 3 in detail;

FIG. 4(b) is a circuit diagram of an actual example of the phase modulation circuit shown in FIG. 4(a);

FIG. 5 is a block diagram showing another embodiment of the inventive apparatus for producing base tones;

FIGS. 6(a) and"(b) are block diagrams respectively showing examples of a circuit construction of stages following the keyers shown in FIG. 5;

FIG. 7 is a block'diagram showing another embodiment of the inventive apparatus for producing base tones;

FIGS. 8(A) and (B) are charts showing waveshapes of modulating signals obtained in the circuit shown in FIG. 7; t

F IGS. 9 and 10 are block diagrams respectively showing other embodiments of the inventive apparatus for producing base tones; 1

FIGS. 11(A) and (B) are charts showing envelopes of the keyed signals from the keyers shown in FIG. 10;

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows a preferred embodiment of the apparatus for producing base tones according to the inven tion. A phase modulation circuit 8 is provided on the output side of an'amplifier 3 for phase-modulating the output signal of the amplifier 3 by a modulating signal of approximately 1 Hz. Reference numeral 9 designates an oscillator which provides a modulating signal of approximately 1 Hz for the phase modulation circuit 8. The output of the phase modulation circuit 8 is fed to )6 frequency dividers 41-43 connected in tandem (cascade). In this and the following-embodiments,a sinusoidal wave of about 1 Hz can most preferably be used as the. modulating signal but other waveshapes may be effectively usedfor'the same purpose. A preferably phase shift to be obtained by this phase modulation is about 300 at the maximum.

FIGS. 4(a) and (b) show an example of the'phase modulation circuit. Since the output of a latching selector 2 typically is a square wave of a small amplitude, this output is amplified to a sufficient degree in the amplifier 3 before it passes to a low-pass filter l 0. The lowpass filter 10 serves to filter the input waveshape to obtain a fundamental wave component. The provision of the low-pass filter 10 is necessary if occurence of difference in the phase shift angle between the fundamental wave component and the harmonic components and between the respective harmonic components in a phase shifting circuit 11 should be avoided. Accordingly, the output of the low-pass filter l0 substantially is a sinusoidal wave. This sinusoidalwave is phaseshifted by the modulating wave from the oscillator 9. The phase-shifted signal is waveshaped into asquare wave by a Schmitt trigger circuit 13. The square wave is better suited to drive /2 frequency dividers consisting, for example, of flip-flops. I

In the above described embodiment, the output of the latching selector 2 is reduced to afundamental wave component by the low-pass filter 10 before it is phase-shifted. This output from the circuit 2 may how ever be direclty phase-shifted without passing through the low-pass filter 10. In this case, difference in the phase shift angle between the fundamental wave component and each harmonic component occurs resulting in a more complicated sway effect.

.FIG. 4(b) illustrates oneactual example of circuit construction of the circuit shown in FIG. 4(a).

FIG. 5 illustratesanother embodiment of the apparatus for producing base tones, according to the invention. In this embodiment, the output signal from the latching selector 2 is amplified in an amplififer 3 and thereafter is fed to two system for producing two different base tones. In one of the systems, the signal is processed in the same manner as in the prior art apparatus. More specifically, the output signal from the amplifier 3 is applied to a frequency dividing circuit consisting of cascade-connected V2 frequency dividers 41a-43a to obtain signals of 4,'8' and 16' registers at the outputs of the respective frequency dividers 41a-43a. These signals of 4', 8' and 16 registers are respectively applied to corresponding keyer circuits 5la-53a the outputs of which in turn are fed to a tone-color circuit. The base tone produced in this system, therefore, has no variation in pitch during its playing. In the other system, the output of signal of the amplifier 3 is applied to a phase modulation circuit 8. in which the signal is phase-modulated by a modulating signal of approximately 1 Hz. An oscillator 9 produces the modulating signal of approximately 1 Hz. A preferably phase difference to be obtained by the phase modulation is about 300 at the maximum. The phase-modulated signal isv divided in frequency by a /2 frequency divider 41b to produce a 4' register signal. The output signal of the A frequency divider'4lb is then divided by a /2 frequency divider 42b to produce an 8 register signal. This 8' signal is further divided by a /2 frequency divider 43b to produce a 16' register signal. These 4', 8 and 16 signals are respectively fed to corresponding tone keyer circuits 51b, 52b and 53b. These keyer circuits 5 lb, 52b and 53b are provided for giving an envelope to the input signal in accordance with depression of a selected pedal. The outputs of the tone keyers 51b, 52 and 53b are applied to a tone-color circuit. Accordingly, phase modulation by approximately 1 Hz is applied to the tone signals passing through this system. Thus, a sway effect is produced in the base tone signal and the pitch is changed by an extremely low frequency wave.

The output signals of the above described two systems may be sounded by separate tone-color circuits and speakers or by common tone-color circuitand speaker. FIG. 6(a) shows an example in which separate tone-color circuits and speakers are provided. The outputs of the keyers 51a 53a are applied to a tone-color circuit 6a, amplified in an amplifier 7a and thereafter are sounded from a speaker a. In the meanwhile,-the outputs of the keyers 51b 53b are applied to a tonecolor circuit 6b, amplified in an amplifier 7b and therafter are sounded from a speaker 10b. In this example, the tone-color circuits 6a and 6b give different tonecolors to the signals applied thereto. FIG. 6(b) shows an example in which a single tone-color circuit 6 is provided. The outputs of the keyers 51a-53a and 51b-53b are all applied to this tone-color circuit 6 to produce a base tone of a desired tone-color. This base tone is amplified in an amplifier 7 and sounded from a speaker FIG. 7 shows another embodiment of the inventive apparatus for producing base tones. The output signal of the latching selector 2 is amplified in the amplifier 3 and thereafter is fed to two systems to obtain base tones respectively from these two systems. In one of the systems, the output signal of the amplifier 3 is applied to a phase modulation circuit 8a in which the signal is phase-modulated by a modulating signal of about 1 Hz. In the other system the output signal of the amplifier 3 is likewise phase-modulated in a phase modulation circuit 8b by a modulating signal of about 1 Hz. It is to be noted that the two modulating signals used in this embodiment differ in phase by 180 from each other. For this purpose, the oscillated output of the oscillator 9 (about 1 Hz) is applied, on one hand, directly to the phase modulation circuit 8b as a modulating signal and is applied, on the other hand, to the phase modulation circuit 80 also as a modulating signal through a phase inverter 12 in which the signal is inverted in phase by 180. FIG. 8(A) shows the modulating signal supplied to the phase modulation circuit 8a and FIG. 8(B) the modulation signal supplied to the phase modulation circuit 8b. A preferable phase shift is about 300 at the maximum.

The phase modulated signal in one system is frequency divided by a frequency divider 41a to produce a 4' signal. Likewise, 8 signal and 16' signal are produced from /2 frequency dividers 42a and 43a respectively. These signals are fed to the tone keyers 51a-53a in which envelopes are given to these signals by depression of corresponding pedals. The outputs of these keyers 51a-53a are applied to a tone-color circuit (not shown) for subsequent sounding from a speaker via an amplifier (not shown). In the other system, 4', 8' and 16' signals are produced by I frequency dividers 4lb-43b. These signals are given suitable envelopes in the tone keyers 51b-53b by depression of corresponding pedals and thereafter are supplied to a tonecolor circuit.

The tone-color circuit, amplifier and speaker may be provided for each system or may be shared by both systems. If they are provided for each system, different tone-colors will be produced by the two systems.

In the present embodiment, phase modulation is carried out in the respective systems at a phase difference at l80 from each other. Accordingly, the phase shift angle of one of the signals which have been phasemodulated in these systems is double that of the other.

Since the signals are sounded simultaneously in the two systems, the sway effect on the pitch is further emphasized.

FIG. 9 shows another embodiment of the apparatus according to the invention. The output of the latching selector 2 is amplified in an amplifier 3 and thereafter is fed to two separate'systems. In one of the systems, the output signal of the amplifier 3 is divided in frequency by a /2 frequency divider 41a to obtain a 4' signal. 8' and 16' signals are likewise obtained by 7% frequency dividers 42a and 43a respectively. These signals are fed to corresponding envelope circuits 51a, 52a and 53a. In the other system, the output signal of the amplifier 3 is applied to a phase modulation circuit 8 in which the signal is phase-modulated by a modulating signal of about 1 Hz. The output of the phase modulation circuit 8 is successively divided in frequency by B frequency dividers 4lb-43b to produce 4', 8 and 16' signals. These registers signals are respectively applied to corresponding tone keyers 51b, 52b and 53b. A fundamental signal constituting the base tone is a 16' signal and the 16' signal from the keyer 53a is supplied to a tone-color circuit 6a. The tone-color circuit 6a also receives the 8' signal which is a harmonic overtone of the 16 signal from the phase modulating system. A tone-color circuit 6b receives the 8 signal from the keyer 52a of the system which does not carry out the phase modulation and the l6'signal from the keyer 53b of the phase modulating system. A tone-color circuit 6c receives the 4 signal from keyers 51a and 51b and the 8 signal from the keyer 52b. The outputs of these tonecolor circuits 6a-6c which have been provided with predetermined tone-colors in these circuits are mixed together at a suitable ratio determined by control of variable resistors R R and R and thereafter is applied to an amplifier (not shown). for subsequent sounding from a speaker. The combinations of the input signals to the respective tone-color circuits are not limited to the above described ones but any combination that includes at least one register signal from the system which does not carry out the phase modulation and at least one signal from the phase modulating system may be employed. A connection selecting switch may be provided between the tone keyers and the tone-color circuits for varying the combinations of signals applied to thetone-color circuits.

The modulating signal is the output of an oscillator 9 (about 1 Hz). The phase shift to be obtained is about 300 at the maximum.

According to the present embodiment the fundamental tone of the base tone sounded from the speaker is stable since it has not been subjected to phase modulation whereas the harmonic overtone which is mixed with the fundamental tone has a sway effect and therefore gives to naturalness the base tone. Moreover, various tone-colors are produced by the combinations of the phase-modulated signals and the signals which have not been subjected to phase modulation. This produces a concerted music effect, i.e., an effect as if a variety of base tone musical instruments were being played together.

FIG. 10 shows another embodiment of the apparatus according to the invention. In this embodiment, characteristics of the tone keyers 51a 53a and 51b 53b are different from those of the tone keyers in the embodiment shown in FIG. 5. The tone keyers 51a 53a in one of the two systems which are operated by depression of the pedals have an envelope characteristic as shown in FIG. 11(A) which rises sharply upon depression of the pedal and sustains at a constant value until it falls sharply upon release of the pedal.

In the other system, the output of an amplifier 3 is applied to a phase modulation circuit 8 in which it is phase modulated by a modulating signal of about 1 Hz. Reference numeral 9 designates an oscillator generating the modulating signal of about 1 Hz. A preferable phase shift to be obtained is about 300 at the maximum. The phase-modulated signalis divided in frequency by 1% frequency dividers 41b, 42b and 43b to produce 4', 8' and 16 signals. These 4', 8' and 16' signals are respectively applied to corresponding tone keyers 51b, 52b and 53b. The tone keyers 51b, 52b and 53b which are operated by depression of the pedals have an envelope characteristic as shown in FIG. 11(B) which rises sharply and starts to decay gradually at next moment. The signal in this system is phase-modulated by the modulating signal of about 1' Hz so that a sway effect is given to the base tone.

The outputs of the tone keyers 51a 53a are mixed together to become tone-colored signals in a tone-color circuit 6a and sounded from a speaker-(not shown) after amplification. The outputs of the tone keyers 51b 53b are also mixed together to make tone-colored signals in a tone-color circuit 6b for subsequent sounding.

As described in the foregoing, the phase-modulated system and the system which is not subjected to phase modulation have different envelope characteristics. This provides the base tone with a sway which is at its maximum when the base tone rises and decreases rapidly thereafter. Since base tones produced by natural musical instruments are unstable due to the sway when they rise and become increasingly stable with the sway decreasing, the base tones obtained by the present embodiment closely resemble those of the natural musical instruments. I

FIG. 12 shows another embodiment of the apparatus according to the invention. The output signal of the latching selector 2 is amplified in .an amplifier 3 and thereafter is successively divided in frequency by /2 frequency dividers 41, 42 and 43. The output of the /2 frequency divider 41 is a 4' signal, the output of the divider 42 an 8' signal, and the output of the divider 43 a 16 signal respectively. These signals are fed to two separate systems as in the several previously described embodiments. In one of the systems, the tone signals are directly supplied to corresponding tone keyers 51a, 52a and 53a. In the other system, the 4' signal is applied to a phase modulation circuit 81, the 8' signal to a phase modulation circuit 82 and the 16' signal to a phase modulation circuit 83 respectively. In' these phase modulation circuits, the tone signals are phasemodulated by a modulating signal 'of about 1 Hz oscillated by an oscillator 9. The 16' signal constitutes a fundamental tone component of the base tone to be obtained, the 8' signal. the second harmonic overtone component, and the 4' signal the fourth harmonic overtone component respectively. The frequency of the '8' signal is twice as high as that of the 16' signal and the frequency of the 4' signal is twice as high as that of the 8' signal. Accordingly, the phase modulation circuits 81, 82 and 83 apply phase modulation to the 4', 8 and 8 nals of 4, 8' and 16' registers are respectively supplied to the tone keyers 51b, 52b and 53b.

The tone keyers 51a 53a and 51b 53b provide the tone signals with predetermined envelopes by operation of the pedals. The outputs of these keyers are applied to a tone-color circuit 6'for giving a desired tonecolor to the base tone and are sounded from a speaker 10 after amplification. The tone-color circuit, amplifier and speaker may be provided in each system separately.

According to the above described construction of FIG. 12, the phase modulation is carried out with a different modulation degree of each foot-register signal. The fundamental tone and harmonic overtones are therefore provided with different sway effects with a result that naturalness and richness are increased.

FIG. 13 shows another embodiment of the apparatus according to the invention. As in the previously de scribed embodiments, the output 'signal of the latching selector 2 is amplified in an amplifier 3 and thereafter is successively divided in frequency by k frequency dividers 41, 42 and 43. The output of the b frequency divided 41 is a 4' signal, that of the divider 42 an 8' signal and that of the divider 43 a 16' signal. These respective foot-register signals are fed to two separate systems. In one of the systems, the signals are directly applied to the tone keyers 51a, 52a and 53a. In the other system, the 4' signal is applied to a phase modulation circuit 81, the 8' signal to a phase modulation circuit 82 and the 16 signal to a phase modulation circuit 83 respectively. A signal of about 1 Hz produced by an oscillator 9 is applied to a phase distributor 13 which produces three modulating signals which differ in phase by 120 from each other as shown in FIGS. 14(A), (B) and (C). These modulating signals are supplied to the phase modulation circuits 81 83.

The 16' signal constitutes a fundamental tone component, the 8' signal a second harmonic overtone component and the '4' signal a fourth harmonic overtone component respectively. The frequency of the 8' signal is twice as high as that of the 16' signal, and the frequency of the 4' signal is twice'as high as that of the 8' signal. Accordingly, the phase modulation circuits 8] 83 apply phase modulation to those respective footregister signals by the same modulating signal but with different modulation degrees. In other words, the

higher the pitch of the base tone, the greater is the sway effect given to the base tone. Further, the modulating signals used in the present embodiment have phase difference among themselves, so that the change of phase in each foot signal is not uniform but very complicated with a result that a concerted music effect, i.e. an effect as if a variety of musical instruments were being played together, is produced.

The phase modulated 4, 8' and 16' signals are respectively fed to the tone keyers 51b, 52b and 53b.

The tone keyers 51a 53a and 51b 53b are operated by operation of the pedals for providing the signals with desired envelopes. The outputs of these tone keyers 51a 53a and 51b 53b are applied to a tone-color circuit 6 in which they are provided with a desired tone-color. The signals are applied to a speaker 10 via an amplifier 7. The tone-color circuits, amplifier and speaker may be provided in each of the system including the keyers 51a 53a and 51b 53b.

According to the embodiment shown in FIG. 13, the

phase modulation is carried out with a different moduis shown in FIG. 16. Since the lation degree for each foot-register signal and the modulating signals have a phase difference among themselves. The fundamental tone and each harmonic overtone are given different sway effects with a greater sway being given to a harmonic overtone of a higher degree. This gives the base tone a complicated sway effect thereby producing a closer semblance to a natural base tone of a natural musical instrument.

FIG. shows another embodiment of the apparatus according to the present invention. The output of the latching selector 2 is amplified in an amplifier 3 and thereafter is successively divided in frequency by /2frequency divider 41, 42 and 43. The output of the /2 frequency divider 41 is a 4 signal, the output of the divider 42 an 8' signal and the output of the divider 43 a 16' signal respectively. These signals are applied to corresponding tone keyers 51 53. The tone keyers 51 53 are triggered by the pedals PK for providing de sired envelopes to these signals. The outputs of these envelope circuits 51 53 are applied to a tone-color circuit 6 for producing a predetermined tone-color. The output signal of the tone-color circuit 6 is applied to a phase modulation circuit 8. The phase modulation circuit 8 carries out the phase modulation by a modulating signal of about 1 Hz supplied from an oscillator 9. An actual example of this phase modulation circuit phase shift angle of the signal which is phase-shifted in the phase modulation circuit is different depending upon the frequency of the signal, the fundamental tone and each harmonic overtone constituting the base tone are phase-modulated with different phase shift angles. The frequency 'com ponents of the output signal of the tone-color circuit 6 are different depending upon the note of the base tone to be sounded and the frequency characteristics of the tone-color circuit itself so that each frequency component has a different phase shift angle. Accordingly, the fundamental tone component and each harmonic overtone component of the base tone respectively having a sway are produced at the output of the phase modulation circuit 8. Since the phaseshift angles of the fundamental wave and the harmonics are different from each other, these waves have different sways and, accordingly, the tone-color as a whole changes periodically thereby producing a signal of a complicated modulated waveshape. If the output of the phase modulation circuit 8 is fed back as shown by a dotted line path to the input side thereof through a-suitable resistance, a more complicated phase modulation will be applied to the signal thereby producing a signal of a more complicated waveshape.

According to the construction shown in FIG. 15, phase modulation is made by a modulating signal of about 1 Hz after a tone-color is imparted to the tone signals. As a result, the phase relations between the fundamental wave component and the respective harmonic components of the base tone are made varied with each component being provided with a different sway. Thus, the base tone with an increased naturalness and variety is produced.

What is claimed is:

1. An apparatus for producing base tones in an electronic musical instrument comprising a latching selector for selecting a single tone signal corresponding to a depressed pedal and, memorizing its selectionuntil a next pedal is depressed, phase modulation means for applying phase modulation to the base tone signal selected by said latching selector by a modulating signal of about 1 Hz, first frequency dividing means for successively frequency dividing the output of said phase modulation means by two to produce a plurality of foot-register signals and first tone keyers for providing each of said foot-register signals with an envelope in accordance with operation of the pedal.

2. An apparatus for producing base tones in an electronic musical instrument as defined in claim 1 in which said phase modulation means comprise an oscillator producing a modulating signal of about 1 Hz, a low-pass filter for filtering said base tone signal, a phase signal circuit which produces phase shift in the base tone signal filtered through said low-pass filter by the modulating signal from said oscillator and a Schmitt trigger circuit which converts the phase-shifted signal to a square wave.

3. An apparatus for producing base tones in an electronic musical instrument as defined in claim 1 which further comprises second frequency dividing means for successively and directly frequency dividing said base tone signal by two and second tone keyers for providing each of the foot-register signals from said second frequency dividing means with an envelope in accordance with operation of the pedal.

4. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 which further comprises a tone-color imparting circuit which provides all the outputs of said first and second tone keyers with a predetermined tone-color.

5. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 which further comprises tone-color imparting circuits each providing the corresponding one of the outputs of said first and second tone keyers with a predetermined tone-color.

6. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 in which said first tone keyers have a sustain envelope characteristic and said second tone keyers have a percussive envelope characteristic.

7. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 in which said first and second tone keyers, respectively produce at least one foot-register signal which is differ-' ent from each other and which further comprises a plurality of tone-color imparting circuits providing the signals with predetermined tone-colors.

8. An apparatus for producing base tones in an electronic musical instrument as defined in claim 1 which further comprises second phase modulation means which applies phase modulation of about 1 Hz to said base tone signal, frequency dividing means for frequency dividing the output of said second phase modulation means by'two to produce a plurality of footregister signals and tone keyers for providing the outputs of said frequency dividing means with an envelope in accordance with operation of the pedal, said first phase modulation means and said second phase m0dulation means carry out the phase modulation by modulating signals which differ in phase by from each other.

9. An apparatus for producing base tones in an electronic musical instrument comprising a latching selector for selecting a single tone signal corresponding to a depressed pedal and keeping its selection until a next pedal is depressed, frequency dividing means for successively frequency dividing the base tone signal selected by said latching selector by two to produce a plurality of-foot-register signals, first tone keyers for directly providing the respective signals with an envelope in accordance with operation of the pedals, phase modulation circuit means for applying phase modulation of about 1 Hz to each of the foot-register signals, second tone. keyers for providing the outputs of said phase modulation circuit means with an envelope and tonecolor imparting means for providing the outputs of said first and second tone keyers with a tone-color.

10. An apparatus for producing base tones in an electronic musical instrument as defined in claim 9 in which said phase modulation circuit means apply phase modulation of the same phase to the respective footregister signals.

1 1. An apparatus for producing base tones in an electronic musical instrument as defined in claim 9 in accordance with operation of the pedals, tone-color imparting means for providing the outputs of said tone keyers with a tone-color, and phase modulation circuit means for applying phase modulation of about 1 Hz to the output signal of said tone-color imparting means. 

1. An apparatus for producing base tones in an electronic musical instrument comprising a latching selector for selecting a single tone signal corresponding to a depressed pedal and memorizing its selection until a next pedal is depressed, phase modulation means for applying phase modulation to the base tone signal selected by said latching selector by a modulating signal of about 1 Hz, first frequency dividing means for successively frequency dividing the output of said phase modulation means by two to produce a plurality of foot-register signals and first tone keyers for providing each of said foot-register signals with an envelope in accordance with operation of the pedal.
 2. An apparatus for producing base tones in an electronic musical instrument as defined in claim 1 in which said phase modulation means comprise an oscillator producing a modulating signal of about 1 Hz, a low-pass filter for filtering said base tone signal, a phase signal circuit which produces phase shift in the base tone signal filtered through said low-pass filter by the modulating signal from said oscillator and a Schmitt trigger circuit which converts the phase-shifted signal to a square wave.
 3. An apparatus for producing base tones in an electronic musical instrument as defined in claim 1 which further comprises second frequency dividing means for successively and directly frequency dividing said base tone signal by two and second tone keyers for providing each of the foot-register signals from said second frequency dividing means with an envelope in accordance with operation of the pedal.
 4. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 which further comprises a tone-color imparting circuit which provides all the outputs of said first and second tone keyers with a predetermined tone-color.
 5. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 which further comprises tone-color imparting circuits each providing the corresponding one of the outputs of said first and second tone keyers with a predetermined tone-color.
 6. An apparatus for producing base tones in an electronic musical instrument as defIned in claim 3 in which said first tone keyers have a sustain envelope characteristic and said second tone keyers have a percussive envelope characteristic.
 7. An apparatus for producing base tones in an electronic musical instrument as defined in claim 3 in which said first and second tone keyers respectively produce at least one foot-register signal which is different from each other and which further comprises a plurality of tone-color imparting circuits providing the signals with predetermined tone-colors.
 8. An apparatus for producing base tones in an electronic musical instrument as defined in claim 1 which further comprises second phase modulation means which applies phase modulation of about 1 Hz to said base tone signal, frequency dividing means for frequency dividing the output of said second phase modulation means by two to produce a plurality of foot-register signals and tone keyers for providing the outputs of said frequency dividing means with an envelope in accordance with operation of the pedal, said first phase modulation means and said second phase modulation means carry out the phase modulation by modulating signals which differ in phase by 180* from each other.
 9. An apparatus for producing base tones in an electronic musical instrument comprising a latching selector for selecting a single tone signal corresponding to a depressed pedal and keeping its selection until a next pedal is depressed, frequency dividing means for successively frequency dividing the base tone signal selected by said latching selector by two to produce a plurality of foot-register signals, first tone keyers for directly providing the respective signals with an envelope in accordance with operation of the pedals, phase modulation circuit means for applying phase modulation of about 1 Hz to each of the foot-register signals, second tone keyers for providing the outputs of said phase modulation circuit means with an envelope and tone-color imparting means for providing the outputs of said first and second tone keyers with a tone-color.
 10. An apparatus for producing base tones in an electronic musical instrument as defined in claim 9 in which said phase modulation circuit means apply phase modulation of the same phase to the respective foot-register signals.
 11. An apparatus for producing base tones in an electronic musical instrument as defined in claim 9 in which said phase modulation circuit means apply phase modulation of different phases to the respective foot-register signals.
 12. An apparatus for producing base tones in an electronic musical instrument comprising a latching selector for selecting a single tone signal corresponding to a depressed pedal and keeping its selection until a next pedal is depressed, frequency dividing means for successively frequency dividing the base tone signal selected by said latching selector by two to produce a plurality of foot-register signals, tone keyers for providing the respective foot-register signals with an envelope in accordance with operation of the pedals, tone-color imparting means for providing the outputs of said tone keyers with a tone-color, and phase modulation circuit means for applying phase modulation of about 1 Hz to the output signal of said tone-color imparting means. 